A paper sheets identification apparatus to determine whether or not the banknotes are genuine and to discern their types is carried in such paper sheet transaction apparatuses as automatic teller machines (ATMs) used in financial institutions and the like and automatic vending machines, for which identification apparatus various techniques to determine whether or not the banknotes are true have been proposed. As one of such techniques, various types of an optical sensor unit to detect the optical characteristics of paper sheets along with the processing method thereof have been proposed to date.
The optical sensor carried in the paper sheets identification apparatus is largely classified into the following two types. One of those types is a sensor unit generally called ‘a point sensor’, in which there are disposed a pair of light emitting element and light receiving unit to detect the optic characteristics of paper sheets in transportation. The other is a sensor unit generally called ‘a line sensor’, which comprises a plurality of linear light receiving elements disposed substantially crosswise to the transportation direction of the paper sheets and a light emitting element unit disposed to emit light substantially along such linear directions of the former to detect the optical characteristics of the paper sheets in transportation. Hereupon, the light emitting element unit, by use of a light emitting element and a light conducting element, is contrived to emit light derived from a small number of light sources universally along such linear directions. As for the point sensor, there is a merit in which such sensor unit is realized as being streamlined in structure and lower in production cost whereas there is a demerit in which the scope to be covered by the same is limited to some of the paper sheets. In comparison, as for the line sensor, it can cover the whole surface of such sheets, so that there is a merit in which a sensor unit higher in detection capability than the point sensor is realized whereas there is a demerit in which its production cost comparatively increases.
Various ideas have been thought up to date for the purpose of keeping such merits intact while minimizing such demerits. For instance, in Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2007-141109), it is proposed that a reflective surface is provided on a portion of the light conducting member and light receiving elements are disposed in plural points opposed to the reflective surface instead of being linearly disposed, thereby, allowing plural portions of the paper sheets to be detected in as streamlined a structure as possible.